The present invention relates to a back-up shear plate for metal frame windows.
Metal frame windows usually include vertically and horizontally oriented elongated hollow bodies with inwardly disposed wall elements (in a direction towards the glass window pane), front and rear wall elements (which may be exterior and interior faces, respectively) and outer wall elements. The outer wall elements are opposite the inwardly disposed wall elements. The inwardly disposed wall elements form an inwardly facing U-shaped or C-shaped channel adapted to retain a window pane therein. The window pane is placed in the U-shaped or C-shaped channel with a gasket, caulk or other type of sealant placed along the front and rear intersecting joints between the U-shaped channel of the metal window frame and the glass pane.
The metal window frame elements, which are the aforementioned elongated hollow bodies, surround the periphery of the window pane. Although reference herein is made to a singular window frame elongated hollow body, the back-up shear plate described herein is used at predetermined locations on each of the horizontal window frame members and vertical window frame members. Typically, back-up shear plates are placed four inches from each corner of the metal window frame and nine inches from the mid-point of each window frame run, that is, nine inches on either side of the center point of the upper and lower horizontal window-frame elements and the left and right vertical window frame elements.
Back-up shear plates are customarily made of aluminum. The aluminum shear plate is extruded to form a base plate having laterally disposed interlockable members (generally female edge members) which interact with the opposing lateral wall elements forming the outwardly facing mouth of the elongated window frame hollow body. The prior art aluminum shear plates are cut in approximately four inch lengths (the longitudinal aspect of the plate) and then placed on a window frame element to cover select portions of the outwardly facing mouth of the metal window frame elongated hollow body member. Prior art aluminum back-up shear plates have a tendency to slide in the mouth of the hollow body frame. Accordingly, installers of windows were required to manually crimp at least two and typically four corners of the aluminum back-up shear plate. Further, prior art aluminum shear plates require two sets of drill bits. The first drill bit is used to drill through the aluminum back-up plate and the second drill bit is used to create a hole for the masonry screw which mounts the metal frame to a concrete column.
Also, prior art aluminum back-up shear plates do not include any self shimming elements. As known in the window installation business, after the rough opening of the window is measured, the metal window frame is constructed from extruded aluminum frame elements and then is installed in the rough opening using back-up shear plates and a plurality of shims. The shims may be wood or other types of readily available construction material. The shims are utilized to level and plum the window in the rough opening and to secure the window in the frame from shear forces. The back-up shear plates are mounted with masonry screws extending through the metal window frames, the back-up shear plates and into the vertical columns and horizontal header and footer to prevent the metal window frame from moving in the rough opening. Shear is an action or stress resulting from applied forces that cause or tend to cause two contiguous parts to slide relative to each other in a direction parallel to their plane of contact.
The present invention solves the problem of utilizing two drill bits, crimping the aluminum back-up shear plate, and, in some instances, provides self shimming structures for the window frame.
It is an object of the present invention to provide a plastic back-up shear plate for metal window frames.
It is another object of the present invention to provide a back-up shear plate which includes self shimming elements.
It is a further object of the present invention to provide a plastic back-up shear plate which includes support ribs for the window pane channel.
It is a further object of the present invention to provide a back-up shear plate which is spring fit into the outwardly facing mouth of the metal window frame in order to avoid further manipulation (crimping) of the shear plate in the metal window frame.
The plastic back-up shear plate is laterally disposed with generally a spring fit into the outwardly facing mouth of a metal window frame. The outwardly facing mouth is formed and defined by the window frame elongated hollow body and particularly by outer wall elements which face each other in an opposing manner. The plastic back-up shear plate has laterally disposed opposite outer edge portions which are interlockable on corresponding outer wall elements of hollow body metal window frame which wall elements define the mouth of the window frame. The plastic back-up shear plate has a lateral dimension slightly larger than the lateral mouth dimension and thereby achieves a spring fit. In one embodiment, the plastic back-up shear plate includes support ribs on its inner base plate face. In another embodiment or a further enhancement of the invention, the outer base face of the plastic back-up shear plate includes at least one, and preferably two, shim elements which rise above the flat outer base face out of the base plane of the plastic back-up shear plate. The shim elements may be configured as arcuate elements spanning a reasonable portion of the flat outer base face. In another refined embodiment, compressible shim elements are fingers having a proximal joint supported on the outer base face and a finger body rising above the outer base face. These finger shims may further include finger pads on distal ends opposite the base joints. The finger bodies may arcuately define a concave form with the outer base face. The finger pads may have a convex arcuate shape as compared to the concaved shaped finger bodies.